A conventionally known method for manufacturing a casting mold using a resin-coated sand, which is prepared by coating a refractory aggregate with a binder such as a heat-curable resin, is a method in which the resin-coated sand is supplied into a cavity of a heated die, the binder is cured by the heat of the die, and the refractory aggregate is bound with the cured binder, whereby the casting mold is manufactured.
With this method, it is possible to manufacture a casting mold having a stable quality with high productivity. However, since the die needs to be heated to a high temperature, the heat-curable resin such as a phenolic resin, which is used as a binder of the resin-coated sand, reacts chemically, and consequently a problem is caused in that toxic substances such as ammonia and formaldehyde are generated, which leads to deterioration in working environment. Further, since a portion of the resin-coated sand, the portion being in contact with the die, is heated rapidly, the manufactured casting mold is likely to suffer distortion such as warpage.
In order to solve these problems, disclosed in Japanese Patent No. 3563973 is a method for manufacturing a casting mold by filling the resin-coated sand inside a die, and blowing steam inside the die, whereby the resin-coated sand inside the die is heated with the steam and a binder therein is cured. In the method, since the resin-coated sand is heated with the heat of the steam, it is possible to prevent the toxic substances from being generated from the resin-coated sand when the same is in contact with the hot die.
However, the steam is supplied into the die through one or, at most, several injection holes arranged in the die. Therefore, if a shape of the casting mold is increasingly complicated, it becomes increasing difficult to allow the steam to be distributed over the entirety of the resin-coated sand filled in the die. Therefore, this technique for manufacturing a casting mold still needs to be improved in order to uniformly heat the entirety of the resin-coated sand filled in the die.